Rotary variable inductor and method of making the same



N. HERMAN ROTARY VARIABLE INDUCTOR AND METHOD OF MAKING THE SAME Filed Nov. 29, 1955 2 Sheets- 1 L fi INVENTOR A/szsolv A RNEY 2,958,057 ROTARY VARIABLE INDUCTOR AND METHOD OF MAKING THE SAME Filed Nov. 29, 1955 N. BERMAN Oct. 25, 1960 2 Sheets-Sheet 2 INVENTOR N 56PM A ORNEY United States Patent O ROTARY VARIABLE INDUCTOR AND METHOD OF MAKING THE SAME Nelson Berman, New Hyde Park, N.Y., assignor, by mesne assignments, to United Aircraft Corporation, East Hartford, 'Conn., a corporation of Delaware Filed Nov. 29, 1955, Ser. No. 549,678

6 Claims. (Cl. 336-135) My invention relates to a rotary variable inductor and method of making the same, and more particularly to a rotary variable inductor, the inductance of which varies linearly as a function of shaft position, and to a method of making the same.

Variable inductors are known in the prior art. For example, the'inductance of a solenoid coil may be varied by moving a slugof magnetic material axially into and out of the coil. Other variable inductors include a first coil disposed within another coil and rotatable on an axis disposed in the plane of the other coil. A variable inductor may also be provided by varying the spacing between a pair of adjacent coils to vary the mutual inductance between the coils. None of these inductors of the prior art provides a means for varying inductance linearly in accordance with shaft position.

I have invented a rotary variable inductor, the inductance of which varies linearly with shaft position. Thus I provide a transducer whose inductance is indicative of shaft position. I have also invented a method by which I form my rotary variable inductor in a simple, rapid and expeditious manner. My method is applicable also to the formation of cores for rotary inductive. couplings.

One object of my invention is. to provide arotary variable inductor, the inductanceof which varies with the position of a shaft.

Another object of my invention is to provide a variable inductor, the inductance of which varies linearly with shaft position.

A further object of my invention is to provide a method of making a rotary variable inductor in a simple, convenient and expeditious manner.

A still further object of my invention is to provide a method of making magnetic cores for rotary magnetic devices.

Other and further objects of my invention will appear from the following description:

In general, my invention contemplates the provision of a rotary variable inductor including a pair of spaced, radially aligned, stationary segmental magnetic core members carrying a pair of series-aiding, connected electrical windings. I dispose a movable segmental magnetic core member in the space between the stationary core members and provide means for rotating the movable member with respect to the stationary members. As the movable core member is moved from a position where its magnetic segments are aligned with the magnetic segments of the stationary core members to a position wherethe respective segments are out of alignment, the inductance of my inductor varies correspondingly between its maximum and minimum limits.

In my method of making my rotary variable inductor I wind a toroidal core winding of magnetic material, such as iron. wire, about a predetermined sector of a temporary or'dummy core. I pot the wound core in a suitable potting material such, for example, as a synthetic resin or plastic. I then cut or saw the potted Patented Oct. 25, teen ice winding either perpendicularly of its axis or annularly to form a pair of stationary core members and a movable core member. I remove the portions of the temporary core from the stationary core members and replace the portions with series-aiding, connected electrical windings. I then dispose the movable core member between the stationary members and provide means for rotating it with respect to the stationary, aligned core members. My method also is applicable to the formation of cores for rotary inductive coupling. In order to form these cores, I merely divide the potted toroidal iron wire winding into two parts, remove the dummy core portions from these parts, replace the portions with electrical windings and mount the core members for rotation with respect to each other.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunctio-n therewith and in which like reference numerals are used to indicate like parts in the various views:

Figure 1 is a perspective view of a toroidal iron wire winding with a part broken away to show the dummy core.

Figure 2 is a perspective view of a segment potted iron wire wound core forming member.

Figure 3 is a perspective view showing the movable and stationary core forming members of one form of my rotary variable inductor.

Figure 4 is a perspective view of one form of my rotary variable inductor.

Figure 5 is a perspective view of a toroidal iron wire winding for forming the core members of a second form of my rotary variable inductor.

Figure 6 is a plan view of a stationary core member formed from the winding shown in Figure 5.

Figure 7 is a plan view of the movable core forming member formed from the winding shown in Figure 5.

Figure 8 is a perspective view, with a part broken away, of a second form of my rotary variable inductor.

Figure 9 is a perspective view of still another form of my rotary variable inductor.

More particularly, referring now to Figures 1 to 4 of the drawings, in order to make my rotary variable inductor, I first form a toroidal winding 10 of a suitable magnetic material, such as iron wire or the like, around a dummy or temporary core 12 which may be made of any suitable nonmagnetic material such, for example, as Wood or the like. After making the winding 10, I pot it in a suitable potting material such, for example, as a synthetic resin or plastic 14.

I divide the potted winding, by sawing or the like, into two semicircular parts for forming a pair of my rotary variable inductors. One of these parts is shown in Figure 2 and is indicated generally by the reference character 16. It will be appreciated that instead of initially forming a 360 winding 10, I may form a 180 winding on a semicircular core and pot this winding to form a member 16. Conveniently, however, I form a full toroidal winding on a complete core 12.

As can be seen by reference to Figure 3, I slit the part 16 perpendicularly of its axis to form respective stationary core members 18 and 20 and a movable core member 22.

As can be seen by reference to Figure 4, I remove the portions of the dummy or temporary core 12 from the stationary core members 18 and 20 and replace them with a pair of D-shaped electrical windings 24- and 26. If desired, I may replace thesportion of core 12 in the movable core forming member with a suitably shaped spacer 28. Conveniently, however, the remaining port-ion of the core '12 may form spacer 28.

Any convenient means such, for example, as a bracket or the like 30, stationarily carries the members 18 and 20 in axially spaced relationship. A conductor 32 connects windings 24 and 26 in series-aiding relation. A pair of conductors 34 and 36 provide electrical connections for my rotary variable inductor. Any convenient means such as a bearing 37 carried by core member 20 supports a shaft 38 for rotary movement with respect to the stationary bracket 30. I form shaft 38 with a hub 40 carrying for rotation with it ring spacer 42 which carries the movable core member 22. It will be seen that the movable core member 22 may be rotated with respect to the stationary core members 18 and 20 to register with them and occupy substantially the same sector. When movable core member 22 is completely within the space between members 18 and 20, and with windings 24 and 26 connected in series-aiding relationship, the inductance between conductors 34 and 36 is a maximum. This will readily be apparent from the fact that, in this relative position of the core members, the iron wire in members 22 reduces the reluctance of the magnetic flux path between windings 24 and 26 to a minimum. As the movable member 22 is rotated out of the space between members 18 and 20, the reluctance of the magnetic flux path between windings 24 and 26 increases and the inductance between terminals 34 and 36 decreases. It is to be noted that, for any particular relative position of the stationary and movable core members, the disposition and orientation of the iron wire in the core members of my variable inductor reduce the reluctance of the magnetic flux path for the flux linking windings 24 and 26, and also reduce losses owing to eddy currents. The construction of my rotary variable reactor is such that the inductance between conductors 34 and 36 varies substantially linearly with the position of shaft 38.

In the form of my invention shown in Figures 1 to 4, the inductance between conductors 34 and 36 varies from maximum to minimum in the course of 180 of rotation of shaft 38. In Figures to 8 I have shown a second form of my invention in which the inductance of my rotary variable inductor varies from maximum to mini mum for 60 of shaft rotation. As can be seen by reference to Figure 5, in this form of my invention I wind spaced iron wire windings 44, each occupying a 60 sec tor, on a dummy ring core 46. As in the form of my invention shown in Figures 1 to 4 I pot windings 44 and core 46 in a suitable plastic potting material 48 After potting, I then slit the assembly perpendicularly of its axis to form stationary core members 50, one of which is shown in Figure 6, and a movable core member 52, shown in Figure 7. I remove the dummy core parts from the stationary core members and replace them with series-aiding connected electrical windings 54. The dummy core portion remaining in movable core member 52 may conveniently form a spacer 56. A shaft 58 carries a member '60 for rotation with it, which member supports the movable core member 52. Conductors 62 and 64 provide electrical connections for this form of my rotary variable inductor. As shaft 58 turns to move movable core member 52 with respect to the stationary core members 50, the inductance between conductors 62 and 64 varies from a maximum to a minimum for 60 of shaft rotation. It will be appreciated from the foregoing that I may form my rotary variable inductor to vary its inductance from maximum to minimum for any desired amount of rotation of a shaft. It is to be noted that the inductance between the output conductors of my rotary variable inductor is a direct measure of shaft position since it varies substantially linearly with shaft position. i

In Figure 9 I have shown a third form of my rotary variable reactor. In this form of my invention I slit a member 16, such as is shown in Figure 2, annularly to form a pair of stationary core members 66 and 68 and a movable core member 70. I remove the dummy core portions from the stationary members 66 and 68 and replace them with respective electrical windings 72 and 74. A conductor 76 connects windings 72 and 74 in series-aiding relation and conductors 78 and 80 provide electrical connections for my inductor. The portion 82 of the dummy core remaining in the movable core member 70 may be left in the member or it may be replaced by a spacer. I mount the movablemember 70 by any convenient means on an arm 84 formed with a hub 86 fixed on a shaft 88 for rotation therewith by means such as a set screw or the like 90. A knurled knob 92 carried by shaft 88 provides a means for rotating the shaft 88 to move member 70 with respect to the stationary core members 66 and 68. With windings 72 and 74 connected in series-aiding relationship, as member 70 is moved from the position shown in Figure 9 in which it lies substantially between members 66 and 68, the inductance between conductors 78 and 80 decreases linearly with shaft position. In the form of my invention shown in Figure 9, the inductance varies from a maximum to a minimum for of rotation of shaft 88. It is to be understood that I may form my inductor with annularly cut movable and stationary core members to vary the inductance of my inductor from maximum to minimum for any selected amount of shaft rotation.

In the practice of my method of making a rotary variable inductor, I first form a toroidal winding on a dummy core, such as winding 10 on core 12. If I wish to have an inductance variation from a maximum to a minimum for 180 of shaft rotation, after potting winding 10 and core 12, I cut the assembly axially to form two semitoroidal members 16, and then cut each perpendicularly to its axis to form two pairs of stationary core members 18 and 20 and two movable core members 22. I remove the portions of core 12 from members 18 and 20 and replace them by respective D-shaped windings 24 and 26. I dispose member 22 between members 18 and 20 and rotatably mount it with respect to members 18 and 20 on a shaft 38. Rotation of shaft 38 through 180 varies the inductance between conductors 34 and 36 from maximum to minimum.

If I desire the inductance of my inductor to vary from a maximum to a minimum in less than 180 of shaft rotation, I form segmental toroidal windings such as windings 44 on core 46. After potting the core 46 and core windings 44, I cut the assembly perpendicularly of its axis to form two stationary core members 50 and a movable core member 52. I remove the portions of core 46 from stationary core members 50 and replace them with windings 54 connected in series. I dispose the movable core member '52 between the stationary core members 50 and mount the movable member 52 on shaft 58 for rotation therewith. In the form of my invention shown in Figures 5 to 8 the inductance between conductors 62 and 64 varies from maximum to minimum through 60 of rotation of shaft 58.

In making the form of my inductor shown in Figure 9 I cut a member, such as member 16, annularly to form stationary core members 66 and 68 and movable core member 70. I remove the portions of the dummy core from members 66 and 68 and replace them with windings 72 and 74. I mount member 70 on a shaft 38 for rotation with respect to members 66 and 68. As shaft 88 rotates through 180, the inductance between conductors 78 and 80 varies linearly from maximum to minimum. As has been pointed out hereinabove, if desired, I may make the inductance of the inductor shown in Figure 9 vary from a maximum to a minimum for any amount of shaft rotation less than 180. This is controlled by the disposition of the toroidal iron wire core forming windings.

It is to be understood that my method is applicable to the formation of core members for other types of rotating electrical magnetic devices. For example, I may .employmymethod to form a stationary and a movable core member for a rotary inductive coupling.

It will be seen that I have accomplished the objects of my invention. I have provided a rotary variable inductor, the inductance of which varies linearly as a function of shaft position. Owing to the disposition of the iron wire in the core members of my inductor for any particular relative disposition of the stationary and movable core members, the reluctance of the magnetic path of my inductor is low and losses owing to eddy currents are small. I have invented a method for forming rotary variable inductors in a simple, convenient and expeditious manner.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. A rotary variable inductor including in combination a pair of stationary core members having substantially co-eXtensive areas of magnetic material, means mounting said stationary core elements in spaced relationship to each other with the areas of magnetic material of the respective members aligned, respective electrical windings carried by said stationary core members, means connecting said electrical windings in series-aiding relationship, a movable core member having an area of magnetic material substantially coextensive with the areas of magnetic material of said stationary core members, and means mounting said movable core member between said stationary core members for movement from a position at which the movable core area of magnetic material registers with the stationary member areas of magnetic material to a position at which the movable member area of magnetic material is out of registry with the stationary member areas of magnetic material to cause the inductance of said windings to vary substantially linearly with the position of said movable core member with respect to said stationary core members.

2. A rotary variable inductor as in claim 1 in which each of said stationary core members comprises a respective portion of a toroidal iron wire winding, said movable core member comprising the remainder of said toroidal iron wire winding.

3. A rotary variable indicator as in claim 1 in which each of said stationary core members comprises a portion of a toroidal iron wire Winding distributed over predetermined segments of the stationary core member, said movable core member comprising the remainder of said toroidal iron wire winding.

4. A rotary variable inductor including in combination a first stationary core member comprising a portion of a toroidal iron wire winding distributed over predetermined segments of said first stationary core member, a second stationary core member comprising a second portion of said toroidal iron wire winding distributed over predetermined segments of said second stationary core member, said portions of the toroidal winding of the stationary core members being aligned with each other, respective electrical windings carried by said stationary core members, means connecting said electrical windings in seriesaiding relation, a movable core member comprising the remainder of said toroidal iron wire winding distributed over predetermined segments of said movable core member, said movable core member being disposed between said stationary core members, means mounting said movable core member for rotary movement with respect to said stationary core member, the arrangement being such that the inductance of said electrical windings is a maximum when the toroidal iron wire winding segments of said movable core member are aligned with the toroidal iron wire winding segments of said stationary core members and a minimum when said movable core segments are out of alignment with said stationary core segments.

5. A rotary variable inductor as in claim 4 in which said toroidal iron wire winding occupies a 180 segment.

6. A rotary variable inductor as in claim 4 in which said toroidal iron wire winding occupies equally spaced spaced segments.

References Cited in the file of this patent UNITED STATES PATENTS 352,105 Zipernowsky Nov. 2, 1886 1,750,149 Zamboni Mar. 11, 1930 1,868,318 Greenidge July 19, 1932 1,988,734 Helgason Ian. 22, 1935 2,585,050 Simon Feb. 12, 1952 2,654,142 Horelick Oct. 6, 1953 FOREIGN PATENTS 537,012 Germany Oct. 29, 1931 1,081,879 France June 16, 1954 

